1. Field of the Invention
This invention relates to an overflow device for a bathtub.
2. Description of the Prior Art
Conventionally, bathtubs are provided with an overflow hole at a level near the top of the bathtub, and the overflow hole is connected to the waste pipe leading from the bathtub. Accordingly, once the level of water reaches the overflow hole, the excess water can drain away to reduce the risk that water will spill over the upper edge of the bathtub and cause a mess and possible damage. Nevertheless, in some cases the overflow cannot cope with the rate of flow required to prevent spillage, for example if the pressure of the water supply to the taps is very high, or if the overflow passageway has become partly or completely blocked. Furthermore, preventing a bathtub from overflowing by draining away the excess water is wasteful of water.
There have been various proposals to deal with these problems. For example, systems are known for automatically opening the normal plug of the bathtub when the water level reaches a predetermined level, but such systems still result in wasted water. Also, electrical systems are known for automatically turning off the supply of water to the bathtub when the water level reaches a predetermined level, but such systems require a supply of electricity and a great amount of care in design and installation to prevent any risk of electrical shock. Furthermore, mechanical systems are known for automatically turning off the supply of water to the bathtub when the water level reaches a predetermined level, but such systems suffer variously from the problems of: bulkiness (see WO099/11876); that they would be difficult to reset when applied to a bathtub (see GB2312838); that reliance is made purely on the buoyancy of a float to provide the motive force to close off the water supply valve(s) (see GB2288330); that they need to be reset by a mechanism that it may be difficult to make accessible in a bathroom scenario (see WO93/09303); or that they are mounted inside the bathtub and need to be connected to the outlet of a conventional bath tap (see JP55042982). The present invention, or at least specific embodiments of it, addresses these problems.